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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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In Reply to: RE: Love the 211 posted by Rocket_Powered on July 2, 2021 at 08:22:41:
It's very difficult to compare these tubes because they can't simply be substituted for each other. And of course, the various amplifiers all use different support components. Even if the amps were otherwise the same, and even if the various systems I've heard used the same preamps, speakers, etc., my listening experiences have been months or years apart. Acoustic memory simply isn't good enough for drawing conclusions.
All that aside, I have gradually grown to favor the 211. I can't point to any great sonic distinction between these two types to support that, but in my opinion, the 211 simply does everything slightly better. One significant technical distinction between the 845 and the 211 has to do with their inherent electrical characteristics. The 845 exhibits a lower amplification factor and thus requires a larger grid swing. For this reason, some people will say it's more difficult to drive. However, the 845 also exhibits a much higher standing grid bias in Class A than the 211, and that ultimately results in greater output power at the point just below grid current. This is evident in the data sheets of the two tubes. While the 845 can output more than 20W with 1,000V on the anode, the 211 is limited to 12W.
For my purpose (and in consideration of the sensitivity of my speakers), 12W simply isn't worth all the trouble and expense necessary to build a stereo amplifier around the 211. There's a solution, but it requires driving the 211 into Class A2. That's a much more complex undertaking than driving the 845 to its maximum output of 20W, a level that I do consider satisfactory and which undoubtedly accounts for its greater popularity. At any rate, this is the reason I have always maintained that the 211 is more difficult to drive.
In the end, I designed my own 211 amps with a totem pole running at more than +500V to achieve the necessary voltage swing. That's followed by a choke loaded, low-Z cathode follower that seamlessly drives the 211 into A2. As with any other 211/845 amplifier, mine operate in pure Class A up to the limit of grid current. Maximum output power is approximately 30W, and this capability comes at no sonic penalty that I can discern.
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Follow Ups
- RE: Love the 211 - Triode_Kingdom 09:30:39 07/02/21 (2)
- RE: Love the 211 - Rocket_Powered 10:08:45 07/02/21 (1)
- RE: Love the 211 - Triode_Kingdom 15:40:28 07/02/21 (0)
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